| Message ID | 1596065445-4630-1-git-send-email-hyun.kwon@xilinx.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift | expand |
Hi Hyun, Thank you for the patch. On Wed, Jul 29, 2020 at 04:30:45PM -0700, Hyun Kwon wrote: > Use switch - case to downshift from the current link rate. It's a small > loop now, so fine to be replaced with switch - case. With a loop, it is > confusing and hard to follow as reported below. > > The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP > DisplayPort Subsystem" from Jul 7, 2018, leads to the following > static checker warning: > > drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure() > error: iterator underflow 'bws' (-1)-2 > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com> > --- > v2 > - Convert the for loop into switch - case > --- > --- > drivers/gpu/drm/xlnx/zynqmp_dp.c | 29 ++++++++++++++++------------- > 1 file changed, 16 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c > index b735072..5d6adeaa 100644 > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c > @@ -567,34 +567,37 @@ static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock, > u8 current_bw) > { > int max_rate = dp->link_config.max_rate; > - u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 }; > + u8 bw_code; > u8 max_lanes = dp->link_config.max_lanes; > u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate); > u8 bpp = dp->config.bpp; > u8 lane_cnt; > - s8 i; > > - if (current_bw == DP_LINK_BW_1_62) { > + /* Downshift from current one */ Maybe "Downshift from the current bandwidth" ? Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > + switch (current_bw) { > + case DP_LINK_BW_5_4: > + bw_code = DP_LINK_BW_2_7; > + break; > + case DP_LINK_BW_2_7: > + bw_code = DP_LINK_BW_1_62; > + break; > + case DP_LINK_BW_1_62: > dev_err(dp->dev, "can't downshift. already lowest link rate\n"); > return -EINVAL; > - } > - > - for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) { > - if (current_bw && bws[i] >= current_bw) > - continue; > - > - if (bws[i] <= max_link_rate_code) > - break; > + default: > + /* If not given, start with max supported */ > + bw_code = max_link_rate_code; > + break; > } > > for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) { > int bw; > u32 rate; > > - bw = drm_dp_bw_code_to_link_rate(bws[i]); > + bw = drm_dp_bw_code_to_link_rate(bw_code); > rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp); > if (pclock <= rate) { > - dp->mode.bw_code = bws[i]; > + dp->mode.bw_code = bw_code; > dp->mode.lane_cnt = lane_cnt; > dp->mode.pclock = pclock; > return dp->mode.bw_code;
Hi Laurent, Thanks for the comment. On Thu, Jul 30, 2020 at 04:12:46PM -0700, Laurent Pinchart wrote: > Hi Hyun, > > Thank you for the patch. > > On Wed, Jul 29, 2020 at 04:30:45PM -0700, Hyun Kwon wrote: > > Use switch - case to downshift from the current link rate. It's a small > > loop now, so fine to be replaced with switch - case. With a loop, it is > > confusing and hard to follow as reported below. > > > > The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP > > DisplayPort Subsystem" from Jul 7, 2018, leads to the following > > static checker warning: > > > > drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure() > > error: iterator underflow 'bws' (-1)-2 > > > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com> > > --- > > v2 > > - Convert the for loop into switch - case > > --- > > --- > > drivers/gpu/drm/xlnx/zynqmp_dp.c | 29 ++++++++++++++++------------- > > 1 file changed, 16 insertions(+), 13 deletions(-) > > > > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c > > index b735072..5d6adeaa 100644 > > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c > > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c > > @@ -567,34 +567,37 @@ static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock, > > u8 current_bw) > > { > > int max_rate = dp->link_config.max_rate; > > - u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 }; > > + u8 bw_code; > > u8 max_lanes = dp->link_config.max_lanes; > > u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate); > > u8 bpp = dp->config.bpp; > > u8 lane_cnt; > > - s8 i; > > > > - if (current_bw == DP_LINK_BW_1_62) { > > + /* Downshift from current one */ > > Maybe "Downshift from the current bandwidth" ? > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > I agree. I'll fix and add the tag. Thanks! -hyun > > + switch (current_bw) { > > + case DP_LINK_BW_5_4: > > + bw_code = DP_LINK_BW_2_7; > > + break; > > + case DP_LINK_BW_2_7: > > + bw_code = DP_LINK_BW_1_62; > > + break; > > + case DP_LINK_BW_1_62: > > dev_err(dp->dev, "can't downshift. already lowest link rate\n"); > > return -EINVAL; > > - } > > - > > - for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) { > > - if (current_bw && bws[i] >= current_bw) > > - continue; > > - > > - if (bws[i] <= max_link_rate_code) > > - break; > > + default: > > + /* If not given, start with max supported */ > > + bw_code = max_link_rate_code; > > + break; > > } > > > > for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) { > > int bw; > > u32 rate; > > > > - bw = drm_dp_bw_code_to_link_rate(bws[i]); > > + bw = drm_dp_bw_code_to_link_rate(bw_code); > > rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp); > > if (pclock <= rate) { > > - dp->mode.bw_code = bws[i]; > > + dp->mode.bw_code = bw_code; > > dp->mode.lane_cnt = lane_cnt; > > dp->mode.pclock = pclock; > > return dp->mode.bw_code; > > -- > Regards, > > Laurent Pinchart
> -----Original Message----- > From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of Hyun > Kwon > Sent: Thursday, July 30, 2020 7:33 PM > To: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Cc: Dan Carpenter <dan.carpenter@oracle.com>; dri- > devel@lists.freedesktop.org; Daniel Vetter <daniel.vetter@ffwll.ch.ch> > Subject: Re: [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate > downshift > > Hi Laurent, > > Thanks for the comment. > > On Thu, Jul 30, 2020 at 04:12:46PM -0700, Laurent Pinchart wrote: > > Hi Hyun, > > > > Thank you for the patch. > > > > On Wed, Jul 29, 2020 at 04:30:45PM -0700, Hyun Kwon wrote: > > > Use switch - case to downshift from the current link rate. It's a small > > > loop now, so fine to be replaced with switch - case. With a loop, it is > > > confusing and hard to follow as reported below. > > > > > > The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP > > > DisplayPort Subsystem" from Jul 7, 2018, leads to the following > > > static checker warning: > > > > > > drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure() > > > error: iterator underflow 'bws' (-1)-2 > > > > > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > > Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com> > > > --- > > > v2 > > > - Convert the for loop into switch - case > > > --- > > > --- > > > drivers/gpu/drm/xlnx/zynqmp_dp.c | 29 ++++++++++++++++------------- > > > 1 file changed, 16 insertions(+), 13 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c > b/drivers/gpu/drm/xlnx/zynqmp_dp.c > > > index b735072..5d6adeaa 100644 > > > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c > > > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c > > > @@ -567,34 +567,37 @@ static int zynqmp_dp_mode_configure(struct > zynqmp_dp *dp, int pclock, > > > u8 current_bw) > > > { > > > int max_rate = dp->link_config.max_rate; > > > - u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, > DP_LINK_BW_5_4 }; > > > + u8 bw_code; > > > u8 max_lanes = dp->link_config.max_lanes; > > > u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate); > > > u8 bpp = dp->config.bpp; > > > u8 lane_cnt; > > > - s8 i; > > > > > > - if (current_bw == DP_LINK_BW_1_62) { > > > + /* Downshift from current one */ > > > > Maybe "Downshift from the current bandwidth" ? > > > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > > > > I agree. I'll fix and add the tag. > Applied to drm-misc-next-fixes. Thanks, -hyun > Thanks! > > -hyun > > > > + switch (current_bw) { > > > + case DP_LINK_BW_5_4: > > > + bw_code = DP_LINK_BW_2_7; > > > + break; > > > + case DP_LINK_BW_2_7: > > > + bw_code = DP_LINK_BW_1_62; > > > + break; > > > + case DP_LINK_BW_1_62: > > > dev_err(dp->dev, "can't downshift. already lowest link rate\n"); > > > return -EINVAL; > > > - } > > > - > > > - for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) { > > > - if (current_bw && bws[i] >= current_bw) > > > - continue; > > > - > > > - if (bws[i] <= max_link_rate_code) > > > - break; > > > + default: > > > + /* If not given, start with max supported */ > > > + bw_code = max_link_rate_code; > > > + break; > > > } > > > > > > for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) { > > > int bw; > > > u32 rate; > > > > > > - bw = drm_dp_bw_code_to_link_rate(bws[i]); > > > + bw = drm_dp_bw_code_to_link_rate(bw_code); > > > rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp); > > > if (pclock <= rate) { > > > - dp->mode.bw_code = bws[i]; > > > + dp->mode.bw_code = bw_code; > > > dp->mode.lane_cnt = lane_cnt; > > > dp->mode.pclock = pclock; > > > return dp->mode.bw_code; > > > > -- > > Regards, > > > > Laurent Pinchart > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c index b735072..5d6adeaa 100644 --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c @@ -567,34 +567,37 @@ static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock, u8 current_bw) { int max_rate = dp->link_config.max_rate; - u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 }; + u8 bw_code; u8 max_lanes = dp->link_config.max_lanes; u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate); u8 bpp = dp->config.bpp; u8 lane_cnt; - s8 i; - if (current_bw == DP_LINK_BW_1_62) { + /* Downshift from current one */ + switch (current_bw) { + case DP_LINK_BW_5_4: + bw_code = DP_LINK_BW_2_7; + break; + case DP_LINK_BW_2_7: + bw_code = DP_LINK_BW_1_62; + break; + case DP_LINK_BW_1_62: dev_err(dp->dev, "can't downshift. already lowest link rate\n"); return -EINVAL; - } - - for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) { - if (current_bw && bws[i] >= current_bw) - continue; - - if (bws[i] <= max_link_rate_code) - break; + default: + /* If not given, start with max supported */ + bw_code = max_link_rate_code; + break; } for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) { int bw; u32 rate; - bw = drm_dp_bw_code_to_link_rate(bws[i]); + bw = drm_dp_bw_code_to_link_rate(bw_code); rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp); if (pclock <= rate) { - dp->mode.bw_code = bws[i]; + dp->mode.bw_code = bw_code; dp->mode.lane_cnt = lane_cnt; dp->mode.pclock = pclock; return dp->mode.bw_code;
Use switch - case to downshift from the current link rate. It's a small loop now, so fine to be replaced with switch - case. With a loop, it is confusing and hard to follow as reported below. The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem" from Jul 7, 2018, leads to the following static checker warning: drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure() error: iterator underflow 'bws' (-1)-2 Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com> --- v2 - Convert the for loop into switch - case --- --- drivers/gpu/drm/xlnx/zynqmp_dp.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-)